Internal combustion engines often experience sudden increase in loads during operation. An engine controller may increase the amount of fuel supplied to the engine during such transient loads in order to maintain engine speed. However, for gaseous fuel engines that burn a homogenous air fuel mixture the rate of increase of fuel supplied to the engine is limited by the rate of increase of air supplied to the combustion and is thereby limited by the rate of increase of intake manifold air pressure of the engine. The engine having a turbocharger may increase the intake manifold air pressure by controlling a compressor. However, the compressor generally takes some time to increase the air pressure due to inherent time needed to increase the speed of the compressor. This may result in a power lag until the air flow increases to the requisite level.
One approach for quickly increasing the intake manifold air pressure is by using an additional air storage unit to provide additional compressed air. This reduces the time needed for increasing power of the engine during sudden load increase. However, additional compressed air introduced in the engine may cause a leaner air fuel ratio which may result in misfiring or improper combustion in the engine.
U.S. Pat. No. 4,864,991 discloses a method for controlling air to gas ratio for a gaseous fuel engine. The method describes increasing the supply of gas and decreases supply of air to have a rich air gas mixture when there is a sudden increase in engine load.